1. Technical Field
The present invention relates to mortars for use with clay or concrete tiles. In particular, it relates to ultra-light sandless mortars for clay or concrete tiles which retain high moisture content that compensates for absorption by dry tiles and enables mortar to retain plasticity for proper hydration and provide time for a strong bond to develop between tile and mortar as well as between mortar and sub-surface.
2. Background Art
For many years the construction industry has utilized both clay and concrete tiles for residential and commercial uses, notably roof covering and floor tiles. The roofing industry has historically utilized job-site-mixed sanded mortar to install the tile on top of the waterproofing membranes previously applied to the roof. The top membrane to which the tile is applied is typically a mineral surfaced roofing-sheet which is normally a 90 lb. per 100 sq. ft. material. More recently tile may be also applied over a "modified bitumen" mineral surfaced roofing using the same mortar application. In the roofing industry the term "mudding" is often used to describe the application of the tile to the roofing membrane with mortar.
The mortar used to apply tile normally consists of the combination of mortar cement and sand in a ratio of approximately three (3) parts sand to one (1) part cement. Specifications generally allow from 2.25:1 to 3:1 maximum sand to cement ratios. The mortar is generally mixed at the job-site in a gasoline or electric powered mortar mixer. The ingredients are bulk delivered sand and bagged tile cement or mortar cement. The mix generally consists of approximately 15 shovels of sand and one eighty (80) lb. bag of mortar cement. Water is added to achieve a consistency that allows good workability. Generally a mix with these qualities, using two (2) trowels of mortar, will allow application of about fifty-five (55) tiles. However, the mix may be extended by the addition of more sand into the mix as well as the use of a lesser amount of mortar per tile. While the term sand is used throughout this disclosure for ease of discussion, those skilled in the art will recognize that sand may include other heavy aggregates, such as gravel and crushed stone.
One of the major problems related to the prior art use of job-site mixed sanded mortars for tile application is the fact that sanded mortars utilize very little water to achieve a desirable consistency or workability for application. Tiles are usually placed in fair weather when the sun is out and the roofing is hot. While the best method of applying tiles is to presoak them in water, the reality of the workplace is that the tiles are usually applied dry and tend to absorb water. In addition to the reduction in mortar moisture caused by dry tiles, a breeze or wind will also tend to dry the mortar. The combination of low water content in sanded mortars; a warm or hot surface; the drying effects of wind; and the absorbency of dry tiles will remove excessive amounts of water from the mortar before the tile has had an opportunity to bond properly to the mortar or the mortar has properly bonded to the roofing prior to the mortar taking a "set" and becoming hardened. The rapid drying may also adversely effect the strength of the mortar since the cement requires the moisture for proper hydration. By its nature, sanded mortar limits the amount of moisture available for the cement hydration process which causes the resulting hardened mortar to have reduced strength.
As a result of these common application problems mortar frequently does not set properly. A consequence of the inadequate setting is the reduced bonding strength of the tiles to the target surface. In turn, inadequate bonding causes premature failure of tiles which ultimately increases the cost of building maintenance. A second disadvantage is the reduced strength of the set mortar due to inadequate hydration.
A consequence of the bonding problems discussed above is the increased level of expense due to bond failure. In normal weather environments, storms can cause extensive damage to roofing tiles and roofs. Further, in areas which are prone to high level winds, such as the southeastern coast of the United States which is periodically exposed to hurricane strength winds, bond failures can result in tiles breaking free from roofs and acting as projectiles. In turn, the exposed underlayment of the roof can fail, causing extensive damage to the entire building. For example, during hurricane Andrew in 1993, many tile roofs were damaged and loosened, causing massive economic damage as well as danger to life and limb of residents. A significant factor in that damage, and a cause of unnecessary structural damage to buildings was the failure of prior art sanded mudding techniques to provide sufficient uplift resistance to prevent tiles from breaking free from roofs, thereby initiating the cycle resulting in complete roof failure. The present commonly used system of tile application with job-site prepared sand mortars, or "mudding" of tile, does not assure that roofs will stay intact during extreme weather conditions such as hurricanes, and in fact, results in unnecessarily high tile failure rates in normal weather conditions.
Another drawback to prior art sanded mortars is the work and safety problems related to the additional weight caused by the sand. Due to the weight of the sand, sanded mortars tend to be very heavy. The high weight contributes to worker injury, especially back problems, when laborers must carry the sanded mortar to the roof for applying roof tiles and even when carrying the mortar for application to floors.
The high weight of sanded mortars also limits the ability to use a greater amount of these mortars beneath the tiles or alternatively to form a complete sublayer between the tiles and the roof underlayment. Because of the stress placed on the roof by the weight of sanded mortar, tiles are typically applied by placing a trowel of mortar on the underlayment and laying a tile on top which results in part of the tile bonding with the mortar and another part of the tile having no contact whatsoever with the mortar. As a result, sanded mortars do not provide a complete bond over the surface of the tile, further exacerbating the problems associated with bond failures by limiting the uplift strength of the resulting bond.
Sanded mortars are typically proportioned at the job site which creates several other drawbacks. Principle among these is the inconsistency of the mortar proportions from batch to batch. When the relative amounts of mortar ingredients vary, whether they vary to stretch an ingredient which is in short supply or they vary because the worker (who may be unskilled) is careless, the hydration, setting time, bonding strength, and hardened mortar strength will vary from batch to batch. The result of this variance is the creation of weak spots in a roof which are more prone to failure than portions of the roof which are held by properly proportioned mortar. A bagged premixed product, manufactured under factory controlled conditions, will eliminate the need for job site proportioning of materials. By so doing, the quality of the resulting tile installation will be more uniform, and the problems discussed above will be reduced.
An addition drawback to site proportioning is the waste material, such as unused sand which must be cleaned up after the job is complete. Of course, the wasted material and the cost of the cleanup adds to the total cost of the tile installation.
Site proportioning and mixing utilizing bulk sand and bags of cement results in higher labor costs; higher equipment maintenance costs; and an environment that can lead to safety problems.
Sanded mortars can be classed in a group described as normal weight mortars. These mortars are typically in the 120 to 145 pound per cubic foot (PCF) range. Known alternative mortars have been developed which improve on the weight problems created by sanded mortars. These mortars fall in a class which can be described as "lightweight" mortars. They include materials such as air-cooled slag, coal cinder, expanded slag, expanded clay, expanded shale, expanded slate, sintered fly ash, scoria, and pumice. While these prior art mortars are "lightweight" as compared to sanded mortars, they in fact carry weight densities of 60 to 125 PCF. Therefore, while improving on sanded mortars, they carry many of the same disadvantages because of their high weight. They have not provided sufficient water holding capacity to allow the best hydration possible while the mortar is setting. In addition, the combination of the reduced amount of roofing mortar which can be used due to weight restrictions, and poor hydration due to insufficient water holding capacity result in reduced bonding and uplift strength than would otherwise be available if a truly lightweight moisture retaining mortar were available.
While addressing the various aspects of tile installation, available mortar compounds have failed to provide a truly lightweight mortar which is capable of retaining sufficient moisture to allow ideal hydration and setting time, reduces risk of worker injury by drastically reducing weight, and allows up to a full bed of mortar to be placed on roofs which in turn provides an insulating layer, increases bonding strength and increases uplift strength.